This invention relates to fluid-delivery systems.
Chesler, U.S. Pat. No. 2,444,004 (xe2x80x9cCheslerxe2x80x9d), describes a writing instrument that includes a rigid body having a cavity, a sac within the cavity, and a ball mounted in a writing tip. The sac includes ink in fluid communication with the writing tip. The cavity further includes a spring that applies pressure to the sac to deliver ink to the writing tip. A rigid bar is positioned between the spring and the sac. According to Chesler (col. 3, lines 20-24):
The pressure exerted by the [spring/rigid bar] is substantially as great when the sac is nearly empty as when it is full, and it is therefore nearly uniform.
Chesler does not explain what he means by xe2x80x9cnearly uniform.xe2x80x9d As will be demonstrated later, the pressure applied by the Chesler spring/rigid bar varies from when the sac is filled to when the sac is empty.
The invention relates to a hand-held fluid delivery system. The system includes a body defining a cavity, a collapsible enclosure within the cavity, and a fluid delivery end in communication with the enclosure. The enclosure includes a fluid such as a correction fluid, ink, glue, or cosmetic product (e.g., nail polish). In the preferred delivery system, the pressure on the fluid is sufficiently consistent that a user will not notice a change in the flow of the fluid from the delivery end during the normal usable life of the system. Moreover, the pressure on the fluid generally is not sensitive to changes in temperature. For example, the pressure on the fluid preferably will not change over a temperature change of 10xc2x0 C. (or even 20xc2x0 C.) within the range of 10xc2x0 C. and 30xc2x0 C. In addition, the preferred delivery system can deliver fluid to a substrate with consistent performance regardless of the orientation of the system and substrate with respect to gravity or in the absence of gravity.
There are a number of aspects to the invention. Four aspects relate to quantitatively defining the constant pressure on the fluid within the collapsible enclosure.
According to a first quantitative definition of constant pressure, the pressure on the fluid does not change more than 20% over at least a 1 ml decrease in the volume of fluid in the enclosure. Preferably, the pressure does not change more than 15%, and more preferably the pressure does not change more than 10%. In addition, preferably the pressure does not change over a 1.5 ml decrease or even a 2.0 ml decrease in the volume of the fluid.
According to a second quantitative definition of constant pressure, the enclosure includes at least 1 ml of fluid and the pressure on the fluid does not change more than 15% after a 50% decrease in volume of the fluid in the enclosure. Preferably, the pressure on the fluid does not change more than 10%, or even 7.5%. Moreover, preferably the pressure on the fluid does not change by these amounts even after a 60%, 70%, and 80% decrease in volume of the fluid in the enclosure.
According to a third quantitative definition of constant pressure, the enclosure includes at least 1 ml of fluid and the change in pressure on the fluid is less than 0.15 psi (preferably less than 0.10 psi) after a 50% decrease (preferably after a 60% or 65% decrease) in volume of the fluid in the enclosure.
And according to the fourth quantitative definition of constant pressure, the enclosure includes at least 1 ml of fluid and the slope of change in pressure in the fluid over change in volume of the fluid is approximately zero during delivery of at least 0.1 ml of fluid, and preferably during delivery of at least 0.2 ml, 0.3 ml, 0.4 ml, and 0.5 ml of fluid.
The hand-held delivery system preferably includes a mechanical element, like a spring (a deformable element that exerts a restoring force), that applies pressure to the collapsible enclosure to deliver fluid from the collapsible enclosure through the delivery end to a substrate. Five aspects of the invention relate to the spring.
In a first aspect of the invention relating to the spring, the pressure applied by the spring decreases less than 25% for a 1 ml decrease in volume of the fluid within the collapsible enclosure. Preferably, the pressure applied by the spring decreases even less (e.g., by less than 20%, 15%, or 10%) for a 1 ml decrease in volume of the fluid within the collapsible enclosure. Preferably, the pressure decreases by less than these amounts for a 1.5 ml or 2 ml decrease in volume of the fluid within the enclosure.
In a second aspect of the invention relating to the spring, the spring is configured to relax no more than 35% during use of the delivery system. The full relaxation of the spring is the difference between the spring position when the collapsible enclosure is fully loaded and the spring position when the spring is fully relaxed outside the pen. Spring position is measured at the point or position of the spring that works against the collapsible enclosure, often through an intervening element such as a shoe, and is measured in the same direction as the compression exerted on the collapsible enclosure. Preferably, the spring is configured to relax no more than 30%, and more preferably no more than 25% or no more than 20%, during use of the delivery system.
In a third aspect of the invention relating to the a spring that is generally arcuate in longitudinal section, the spring has two arms that make up the total length of the spring. This means that the arms are joined directly at a central point without an intervening segment. During use of a hand-held fluid delivery system including the spring, the pressure is applied to the collapsible enclosure by a central portion of the spring (preferably through a shoe).
In a fourth aspect of the invention relating to the spring, the spring again has two arms. Each arm has a free end, and each arm is generally tapered in width towards the free end. The tapered design assists in maintaining the most nearly constant pressure on the enclosure during dispensing of the deliverable fluid.
In a fifth aspect of the invention relating to the spring, the spring has an essentially uniform distribution of surface stress over most (greater than 80%) of the spring during use of the delivery system.
The hand-held delivery device including the spring also preferably includes a shoe between the spring and the collapsible enclosure. The shoe has a pressure applicator surface that contacts the enclosure, and in a further aspect of the invention the applicator surface has a beveled end towards the fluid delivery end. The beveled end helps maintain fluid communication between the enclosure and the delivery end as the enclosure collapses during use.
In another aspect of the invention, the collapsible enclosure includes a fusible portion that can be fused (e.g., heat fused) to the fluid delivery end to provide a stable fluid communication path. The enclosure may be composed of more than one layer, and when it is composed of more than one layer preferably the inner layer is composed of the fusible material.
The delivery tip may include a ball, a porous capillary tip, or the tip used with a poppet valve, as described, for example, in JP 62-29103, JP 62-35883, or JP 62-35884.
In another aspect of the invention, the delivery system includes a valve in the delivery end that seals the delivery end when the device is not in contact with a substrate. The valve may be, for example, a poppet valve, a spring-loaded ball, or a porous tip valve. An example of a porous tip valve is described in U.S. Pat No. 4,913,175, which is incorporated by reference. The valve preferably is a spring-loaded ball, such as described in WO 97/03845, U.S. Pat. No. 5,277,510, and U.S. Pat. No. 5,056,949, all of which are incorporated by reference.
The invention also relates to using the hand-held delivery system to deliver fluid to a substrate. The invention also relates to methods of producing the hand-held delivery system.
Fluid, as used herein, includes liquids and any other flowable compositions (e.g., gels and creams) that are capable of flowing under pressure from the collapsible enclosure through the delivery end to a substrate.
Other features and advantages of the invention will be apparent from the description of the preferred embodiment thereof, and from the claims.